Issue 81

LEO Labs Reports Near Miss

13 Sep 2023: A derelict Soviet-era payload (Cosmos 807) had a conjunction with a Chinese rocket body. The miss distance was 36 m (± 13 m) and the probability of collision was 1E-3 (i.e., 0.1% or 1/1,000). Cosmos 807 and CZ-4C had a combined hard body radius (HBR) of 5.6 m. This contributed to the relatively large…

13 Sep 2023: A derelict Soviet-era payload (Cosmos 807) had a conjunction with a Chinese rocket body. The miss distance was 36 m (± 13 m) and the probability of collision was 1E-3 (i.e., 0.1% or 1/1,000). Cosmos 807 and CZ-4C had a combined hard body radius (HBR) of 5.6 m. This contributed to the relatively large probability of collision (PC) value. If these two objects had collided, the number of resulting cataloged fragments would have likely been ~3,000. By comparison the 2021 Russian ASAT test resulted in ~1,800 total cataloged fragments over time.

– Cosmos 807 is a 400 kg payload launched into an elliptical orbit in 1976. It’s likely Cosmos 807 has had many close encounters with other objects over time.

-Cosmos 807 has an apogee of 1,126kms and a perigee of only 366kms…it is regularly traversing 760kms of trafficked space.

– In the last 20 months, LEO Labs has observed 50 high-PC (i.e., PC > 1E-6) conjunctions involving Cosmos 807. While the majority were with operational payloads, 14 included fragments – 6 of which were from the fragment cloud generated after Russia’s 2021 ASAT test.

-The Chinese CZ-4C Rocket Body (R/B) is a 2,000 kg object abandoned five years ago – and it’s already been involved in 141 high-PC conjunctions, split almost equally between fragments and operational payloads.

-The CZ-4C R/B has an apogee of 682kms and a perigee of 553kms.

COSMOS 807 conjunction history

CZ-4C rocket body conjunction history

Near miss between 400 kg Cosmos 807 and 2,000 kg CZ-4C rocket body on 13 September 2023